Comparative Study On The Methods For Determining Hydrogeological Parameters In Leaky Confined Aquifers By Transient Flow Pumping Test

Groundwater, as an important component of water resources, plays an important role in the national economic construction and development. Hydrogeological parameters are the basis for groundwater resources evaluation, aquifer pollution risk assessment and groundwater flow and solute transport numerical simulation, of which the accuracy is closely related with the reliability of hydrogeological parameters. Based on the non-steady flow theory of leaky confined aquifers, the paper describes the theories, methods and steps for calculating the various hydrogeological parameters of leaky confined aquifers using the standard curve fitting method, inflection point method, the entire curve fitting method and numerical simulation method. Taking the pumping test in hydrogeological investigation project in Shizuishan city as an example, these methods were used to calculate the parameters in the investigation area and comparative analysis was carried out with regard to the calculation principles, processes and results. The whole thesis can be divided into three main parts as follows:The first chapter is the introduction in which the author outlines the purpose and significance of the study, describes the advancement of analytical methods and numerical methods in the calculating hydrogeological parameters, and points out the necessity of studying on the methods for calculating the hydrogeological parameters.In the second chapter, after a brief introduction to the first class of the more well flow model flow system, based on the details of the use of non-steady flow pumping confined aquifer test data to solve the various methods of hydrogeological parameters of the principles and steps for the actual project hydrogeological parameters in the solution provides a theoretical basis.The third part includes chapter three and chapter four. In this part, the non-steady flow pumping test carried out in the No.2 water source site of Shizuishan city was taken as an example, and the standard curve fitting method, inflection point method, the entire curve fitting method and numerical simulation method were respectively used to calculate the aquifer parameters. These methods were compared and analyzed from the calculation process, calculation results and suitability in practical uses, and the following conclusions were obtained:1. The standard curve fitting method, inflection point method, the entire curve fitting method and numerical simulation method can all be applied in calculating the hydrogeological parameters of leaky confined aquifer system. The results are basically similar, but advantages and disadvantages exist in the calculation process, the results accuracy and method practicability of different methods.2. Extensive comparative analyses show that the inflection point method is at disadvantage in calculation processes, calculation results and suitability in practical uses compared with the other three methods. As a chart-based method, in spite of relatively lower pumping test requirements, the inflection point method involves much human interference during the calculation and the calculation results differs to a great extent from the real values.3. The standard curve fitting method, as the most basic method for hydrogeological parameters calculation, plays a significant role in parameters determination. With the development of automatic curve fitting software, it will still be widely used for hydrogeological parameters calculation. There is also certain human interference in the processes with standard curve fitting method, but the interference are much weaker compared with the inflection point method.4. Entire curve fitting method is based on the analytical solution of well flow and optimization fitting theory. The calculation process is little influenced by human interference and the accuracy and reliability of the results is higher. Its biggest advantage is the full use of all the pumping data and recovery data to ensure the uniqueness of the results. The calculation principle is simple to understand, and the calculation process is also very easy to implement. It can be used for confined aquifer and phreatic aquifer with broad application prospects. The development of related software will further promote the development. of the theory and application of the method. However, it has higher requirements for pumping test.5. In nature, there is no place tallying exactly with the same assumptions. Many errors will occur when analytical solutions and conceptualizations are carried out, because analytical solution can not perfectly describe the actual groundwater flow in field. However, groundwater flow numerical simulation can take into account many factors impacting the groundwater flow field. It can be expected that numerical simulation will play an increasing role in groundwater system identification. However, in small-scale hydrogeological investigation, the numerical simulation method requires more work and the processes of parameter adjustment require a longer computing time. Therefore, numerical simulation method is recommended in complex hydrogeological system.The results of the study are of great practical and theoretical significance in rational groundwater resources exploitation and groundwater pollution control and protection.